1. Field of Invention
The field of the currently claimed embodiments of this invention relates to micromanipulation systems and methods.
2. Discussion of Related Art
Arguably the most technically demanding field of ophthalmic surgery, vitreoretinal practice has faced significant challenges due to present technical and human limitations. A prototypical vitreoretinal task is membrane peeling, where the surgeon delaminates a very thin fibrous membrane adherent to the retinal surface, using either a pick or micro-forceps. Successful execution of this task requires extensive experience, and is extremely difficult to master due to suboptimal visualization, inconsistent tissue properties, the surgeon's physiological hand tremor, fatigue and involuntary patient motion. During the operation, the instruments need to be moved very slowly, within a range of 0.1-0.5 mm/s, in an extremely delicate environment. Furthermore, application of excessive forces should be avoided. The required forces for delamination routinely lie below the surgeon's sensory threshold. These forces were shown to be below 7.5 mN in porcine cadaver eyes and only 19% of events with this force magnitude can be felt by surgeons [1]. Unintentional motion and application of excessive forces can damage retinal veins [2] and give rise to serious complications such as iatrogenic retinal breaks [3], vitreous hemorrhage, or subretinal hemorrhage [4] leading to potentially irreversible damage and loss of vision.
Retinal vein cannulation (RVC) proposes to treat retinal vein occlusion by direct therapeutic agent delivery methods. During the procedure, clot-dissolving plasminogen activator (t-PA) is injected into the occluded vein [5]. The fine, sharp tips of drawn glass micropipettes enable injection into very small veins. However, their transparency and fragility result in visibility and safety issues. As a more rigid and visible alternative, stainless steel microneedles were proposed [6]. Tests on porcine eyes showed that microneedles are more feasible instruments for microvascular surgery than the glass micropipettes, which was further supported by successful clinical demonstrations on human retinal veins [7]. Despite these improvements, visualizing the tool tip using the operating biomicroscope is still not trivial, and the operation still requires accurate manipulation of extremely delicate tissues inside of the eye, which puts RVC at the limits of human performance.